Longitudinal study of delayed reproductive success in a pair of white-cheeked gibbons (Hylobates leucogenys)

Abstract

Concern over a lack of breeding success in a pair of white-cheeked gibbons (Hylobates leucogenys) prompted a four-part study of gibbon behavior and physiology at the Lincoln Park Zoo. Data were collected to determine the female intermenstrual interval (IMI) and identify periods of peak receptivity. Subsequent behavioral data were gathered during both female menses and estrous periods to formulate a behavioral profile for each gibbon. The female experienced a species-typical IMI of 21.6 days and exhibited heightened levels of behavioral receptivity toward the male during estrus. The male exhibited high levels of human-directed behavior throughout the day. Closing the exhibit to visitors did not result in higher levels of social proximity or prosocial behavior between the pair, although it did eliminate the male's human-directed behavior during the experimental condition only. The female exhibited higher levels of social grooming, solicitation of the male, and proximity to the male when the pair was locked indoors. Based on those findings, the pair was moved to an exclusively indoor exhibit. The female's visibility to the public decreased substantially in the alternate exhibit, but there were no other significant behavioral changes. Nearly one year after the exhibit change, the female gibbon was confirmed to be pregnant. Although the results of this study cannot be used to infer causal conditions that resulted in the pregnancy, they do support the notion that systematic documentation of animal behavior and physiology may be used as a tool for monitoring reproductive behavior and informing management decisions. © 2002 Wiley-Liss, Inc.